There are a wide variety of safety concerns regarding swimming, particularly at swimming pools, water parks, and beaches. In many instances, despite the presence of life guards, help for a swimmer in trouble comes far too late to prevent drowning. Even with adequate staffing numbers, lifeguards often find it difficult to monitor, effectively and safely, large numbers of swimmers.
There have been numerous attempts at developing automatic alarm equipment to warn of swimmers in danger. Several inventions have focused on protecting children and non-swimmers from drowning in backyard swimming pools (See e.g., U.S. Pat. Nos. 3,953,843; 3,969,712; 4,079,364; 4,121,200; 4,187,502; 4,747,085; 5,049,859). These devices typically monitor for the undesired presence of a body in a swimming pool such as from a slip or fall. However, these devices are often not effective for monitoring active swimming areas where persons have intentionally entered the water.
Other swimmer safety devices address the protection of scuba divers (See e.g., U.S. Pat. No. 4,307,449). Many of these devices operate simply by measuring the total amount of time in the water, or by measuring the amount of time spent at a given depth. For example, measuring the duration of a scuba dive (U.S. Pat. No. 4,307,449), or monitoring the time period of a scuba diver's maximum depth (See e.g., U.S. Pat. No. 4,336,591). Unfortunately, these devices do not determine whether a swimmer is in distress or experiencing other difficulties. Nor are these devices useful for determining the location of a swimmer.
Some devices for detecting a swimmer in the water are known. Many of these detection methods rely on some variation of an acoustic or sound based technique. For example, U.S. Pat. No. 4,337,527 describes a system that uses ultrasonic transmission through the water to identify underwater targets. A human operator listening to the headphone output classifies the target and determines its location. U.S. Pat. No. 4,459,689 describes an apparatus utilizing combination energy transmitting and receiving transducer for detecting and locating objects within a plurality of zones. U.S. Pat. No. 4,635,242 describes an underwater signaling device utilizing acoustic sound generators. However, these devices are not capable of monitoring crowded swimming environments.
A few devices for detecting swimmers in distress are known. (See e.g., U.S. Pat. Nos. 4,932,009 and 5,097,254 describe systems for detecting distressed swimmers). However these inventions use acoustic transducers rather than electromagnetic antennas. Furthermore, these devices do not pinpoint the location of distressed swimmers.
U.S. Pat. No. 5,019,822 entitled Marine Object Detector describes a system that uses low frequency electromagnetic transmission through the water and measures amplitude and phase anomalies caused by intruding swimmers in a protected area. This patent has the objective of protecting bridges, piers etc. of military importance from being destroyed by explosive charges. However, this invention only monitors the presence of an undesired swimmer and does not permit the monitoring of swimmers in areas where their presence is desired.
Therefore, of particular interest is the development of a system for monitoring large numbers of swimmers in a swimming pool, beach area, or water park. Such a system would be capable not only of monitoring the swimming status of a large number of swimmers, but would also be capable of pinpointing the exact location of a swimmer in distress with sufficient warning to permit a timely rescue.
All references cited herein are incorporated by reference.